2003/01/10 by L. Binette, Luc Binette, Binette, Luc +8 · 1 citation
Chemistry · Physics and Astronomy · #Advanced Chemical Physics Studies #Astrophysics (astro-ph) #FOS: Physical sciences #Spectroscopy and Laser Applications #Spectroscopy and Quantum Chemical Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0301180
15 pages, 6 figures, submitted to Revista Mexicana de Astronomia y Astrofisica, revised version
arxiv created 2003/01/10 · openalex publication_date 2003/01/10 · arxiv updated 2009/12/01 · openalex created_date 2022/08/28 · openalex updated_date 2026/07/28
The magnitude of the temperature fluctuations (t2) required to explain the\nobserved inconsistencies between metallicities inferred from recombination\nlines and from forbidden lines cannot be attained by steady-state equilibrium\nphotoionization models. If on the other hand the nebular ionizing source was\nvariable, the temperature fluctuations t2 would be significantly larger. We\ninvestigate the time-dependent response of the nebular ionization and\ntemperature structure when photoionized by a periodically varying source. We\nstudy how the asymptotic mean value, <t2>, behaves as a function of the period\nor amplitude of the source variability. We find that the temperature\nfluctuations occur only in the outer section of the nebula, close to the\nionization front, within a zone corresponding to 8-20% of the ionized layer's\nthickness. We conclude that the amplitude of the exciting star variations\nrequired to achieve a <t2> = 0.025 (as in the Orion nebula) is unacceptably\nlarge. Source variability is therefore not a viable mechanism to explain the\nobserved values of t2. We reach a similar conclusion from studies of the\ntemporal variability resulting from intermittent shadows behind opaque\ncondensations. We find that photoionized nebulae are on average less massive\nbut somewhat hotter in the case of cyclicly variable ionizing sources.\n